History's Most Destructive Volcanoes

The June 12, 1991 eruption column from Mount Pinatubo taken from the east side of Clark Air Base.

Credit: USGS

The eruption of a volcano on the island nation of Iceland on
Saturday is a result of the tectonic processes that have continuously shaped
and re-shaped the Earth's surface for billions of years. These processes are
responsible for some of the biggest, deadliest eruptions in history.

The Eyjafjallajokull (AYA-feeyapla-yurkul) volcano — part of the
volcanic complex that originally formed
Iceland — erupted on March 20 for the first time in nearly 200 years. While
the eruption has not been a major one so far, it did cause residents in the
surrounding areas to evacuate, as they wait to see if the volcano will continue
to spew lava and ash or quiet back down.

Other residents of volcanically active areas, whether
prehistoric creatures or modern humans, haven't always had enough warning to
escape before a nearby volcano blew its top, sometimes virtually destroying
everything for many miles around.

Here are some of the biggest, most destructive volcanic
eruptions on Earth:

Deccan Traps – Deccan
Plateau, India – about 60 million years ago

The Deccan Traps are a set of lava beds in the Deccan
Plateau region of what is now India that cover an area of about 580,000 square
miles (1.5 million square kilometers), or more than twice the area of Texas.
The lava beds were laid down in a series of colossal volcanic eruptions that
occurred between 63 million and 67 million years ago.

The timing of the eruptions roughly coincides with the
disappearance of the dinosaurs, the so-called K-T mass extinction (the
shorthand given to the Cretaceous-Tertiary extinction). Evidence for the
volcanic extinction
of the dinosaurs has mounted in recent years, though many scientists still
support the idea that an asteroid impact did the dinosaurs in.

Yellowstone
Supervolcano – northwest corner of Wyoming, United States – about 640,000 years
ago

The history of what is now Yellowstone National Park is
marked by many enormous eruptions, the most recent of which occurred about 640,000
years ago, according to the United States Geological Survey. When this gigantic
supervolcano
erupted, it sent about 250 cubic miles (1,000 cubic kilometers) of material
into the air. The eruptions have left behind hardened lava fields and calderas,
depressions that form in the ground when material below it is erupted to the
surface.

The magma chambers thought to underlie the Yellowstone
hotspot also provide the park with one of its enduring symbols, its
geysers, as the water is heated up by the hot magma that flows underneath the
ground.

Some researchers have predicted that the supervolcano will
blow its top again, an event that would cover up to half the country in ash up
to 3 feet (1 meter) deep, one study predicts. The volcano only seems to go off
about once every 600,000 years, though whether it ever will happen again isn't
known for sure. Recently though, tremors have been recorded in the Yellowstone
area.

While the date of the eruption isn't known with certainty, geologists
think that Thera
exploded with the energy of several hundred atomic bombs in a fraction of a
second. Though there are no written records of the eruption, geologists think
it could be the strongest explosion ever witnessed.

The island that hosted the volcano, Santorini (part of an
archipelago of volcanic islands), had been home to members of the Minoan
civilization, though there are some indications that the inhabitants of the
island suspected the volcano was going to blow its top and evacuated. But
though those residents might have escaped, there is cause to speculate that the
volcano severely disrupted the culture, with tsunamis and temperature declines
caused by the massive amounts of sulfur dioxide it spewed into the atmosphere
that altered the climate.

Mount Vesuvius –
Pompeii, Roman Empire (now Italy) – 79

Mount Vesuvius is a so-called stratovolcano that lies to the
east of what is now Naples, Italy. Stratovolcanoes are tall, steep, conical
structures that periodically erupt explosively and are commonly found where one
of Earth's plates is subducting below another, producing magma along a
particular zone.

Vesuvius' most famous eruption is the one that buried the
Roman towns of Pompeii and Herculaneum in rock and dust in 79, killing
thousands. The ashfall preserved some structures of the town, as well as
skeletons and artifacts that have helped archaeologists better understand
ancient Roman culture.

Vesuvius is also considered by some to be the most
dangerous volcano in the world today, as a massive eruption would threaten
more than 3 million people who live in the area. The volcano last erupted in
1944.

Laki – Iceland – 1783

Iceland has many volcanoes that have erupted over the course
of history. One notable blast was the eruption of Laki volcano in 1783.

The eruption freed trapped volcanic gases that were carried
by the Gulf Stream over to Europe. In the British Isles, many died of gas
poisoning. The volcanic material sent into the air also created fiery
sunsets recorded by 18th-century painters. Extensive crop damage and
livestock losses created a famine in Iceland that resulted in the deaths of
one-fifth of the population, according to the Smithsonian Institution's Global
Volcanism Program.

The volcanic eruption, like many others, also influenced the
world's climate, as the particles it sent into the atmosphere blocked some of
the sun's incoming rays.

Tambora – Indonesia -
1815

The explosion of Mount Tambora is the largest
ever recorded by humans, ranking a 7 (or "super-colossal") on the
Volcanic Explosivity Index, the second-highest rating in the index. The
volcano, which is still active, is located on Sumbawa Island and is one of the
tallest peaks in the Indonesian archipelago.

The eruption reached its peak in April 1815, when it
exploded so loudly that it was heard on Sumatra Island, more than 1,200 miles (1,930
km) away. The death toll from the eruption was estimated at 71,000 people, and
clouds of heavy ash descended on may far-away islands.

Krakatoa – Sunda
Strait, Indonesia – 1883

The rumblings that preceded the final eruption of Krakatoa
(also spelled Krakatau) in the weeks and months of the summer of 1883 finally
climaxed into a massive explosion on April 26 - 27. The explosive eruption of
this stratovolcano, situated along a volcanic island arc at the subduction zone
of the Indo-Australian plate, ejected huge amounts of rock, ash and pumice and
was heard thousands of miles away.

The explosion also created a tsunami, whose maximum wave
heights reached 140 feet (40 meters) and killed about 34,000 people. Tidal
gauges more than 7,000 miles (about 11,000 km) away on the Arabian Peninsula
even registered the increase in wave heights.

While the island that once hosted Krakatoa was completely
destroyed in the eruption, new eruptions beginning in December 1927 built the
Anak Krakatau ("Child of Krakatau") cone in the center of the caldera
produced by the 1883 eruption.

Novarupta - Alaska
Peninsula – June, 1912

The eruption of Novarupta
— one of a chain of volcanoes on the Alaska Peninsula, part of the Pacific Ring
of Fire — was the largest volcanic blast of the 20th century. The powerful
eruption sent 3 cubic miles (12.5 cubic km) of magma and ash into the air,
which fell to cover an area of 3,000 square miles (7,800 square km) more than a
foot deep.

The blast was so powerful that it drained magma from under
another volcano, Mount Katmai, six miles east, causing the summit of Katmai to
collapse to form a caldera half a mile deep.

Mount St. Helens –
Washington state, United States – 1980

Mount St. Helens, located about 96 miles (154 km) from
Seattle, is one of the most active volcanoes in the United States. It's most
well-known eruption was the May 18, 1980 blast that killed 57 people and caused
damage for tens of miles around. Over the course of the day, prevailing winds
blew 520 million tons of ash eastward across the United States and caused
complete darkness in Spokane, Wash., 250 miles from the volcano.

The stratovolcano blasted a column of ash and dust 15 miles
(24 km) into the air in just 15 minutes; some of this ash was later deposited
on the ground in 11 states. The eruption was preceded by a magma bulge on the
north face of the volcano, and the eruption caused that entire face to slide
away — the largest landslide on Earth in recorded history.

In 2004, the peak came
back to life and spewed out more than 26 billion gallons (100 million cubic
meters) of lava, along with tons of rock and ash.

Mount Pinatubo –
Luzon, Philippines – 1991

Yet another stratovolcano located in a chain of volcanoes
created in a subduction zone, the cataclysmic eruption of Pinatubo was a
classic explosive eruption.

The eruption ejected more than 1 cubic mile (5 cubic
kilometers) of material into the air and created a column of ash that rose up 22
miles (35 km). Ash fell across the countryside, even piling up so much that
some roofs collapsed under the weight.

The blast also spewed millions of tons of sulfur dioxide and
other particles into the air, which were spread around the world by air
currents and caused the global temperatures to drop by about 1 degree
Fahrenheit (0.5 degree Celsius) over the course of the following year.

Andrea graduated from Georgia Tech with a B.S. in Earth and Atmospheric Sciences in 2004 and a Master's in the same subject in 2006. She attended the Science, Health and Environmental Reporting Program at New York University and graduated with a Master of Arts in 2006.